is a symptom frequently met with in early life. The term does not denote merely increased rapidity of breathing. The respiratory move ments may be hurried without the patient's being sensible of any unusual effort in the act of breathing or of suffering from imperfect aeration of the blood. To constitute dyspncea there must be perceptible distress ; and the term may be defined as a conscious embarrassment in the performance of the respiratory function.
Dyspncea is by no means confined to cases of pulmonary mischief ; in deed, in the child, extreme difficulty and labour of breathing, with great lividity of face, although possibly produced by disease of the lung, is yet more commonly the consequence of some other cause. The most urgent and alarming form of dyspncea is seen in cases of impediment to the pas sage of air through the glottis. We find it carried to its highest point in stridulous and membranous laryngitis, in obstruction of the windpipe by a foreign body, in extra laryngeal pressure from an abscess in the pharynx, and in pressure upon the trachea or a large bronchus by a mass of enlarged glands. Again, intense clyspncea may be found in a case where air pene trates freely into the lungs. If the circulation through the pulmonary vessels is obstructed, as when a clot is slowly forming in the pulmonary artery, the suffering from deficient aeration of blood may amount to an agony. So, also, in serious disease of the heart dyspncea is a common symptom, for the passage of blood through the lungs is impeded by the valvular lesion.
Again, external pressure upon the lung will excite a very pronounced feeling of dyspncea. When one lung is entirely compressed, and the heart dislocated by a copious liquid effusion into the pleura, dyspncea may be urgent and threaten actual suffocation. When the ribs are greatly soft ened, as in a case of advanced rickets, the pressure of the atmosphere upon the yielding chest-walls may cause such impediment to the expansion of the lungs that serious dyspncea, may be induced. If at the same time the de
scent of the diaphragm is impeded by accumulation of flatus in the belly, the danger is really imminent. On the other hand, in cases of actual pul monary mischief clyspncea is not always present. We find it, indeed, in catarrhal pneumonia and bronchitis, especially if the latter disease is ac companied by any occlusion of the tubes ; but in other cases of interfer ence with the pulmonary function it is exceptional to see signs of suffering from conscious want of air carried to an extreme degree. Even in ad vanced phthisis distress from this cause is rarely great ; and in croupous pneumonia and collapse of the lung the respirations, although greatly quickened, are accompanied by little or no exaggeration of movement, and dyspncea in the sense of an active feeling of oppression of the chest cannot be said to exist.
In every case of dyspncea we have, therefore, to examine very carefully in order to discover the cause to which the impediment to respiration may be correctly attributed. As a rule, perhaps, dyspncea is irregular in its severity. It is subject to temporary increase and diminution,- so that the patient from a condition of great distress may pass into a state of com parative ease. The term "paroxysmal dyspncea" is, however, confined to cases where the difficulty of breathing occurs in attacks of variable sever ity, which last a longer or shorter time and then pass completely away.
There are certain rare causes of remittent dyspncea in the child which may be mentioned. These are—paralysis of the respiratory muscles and of the diaphragm, such as may occur as a sequel of diphtheria (see page 100) ; interstitial oedema of the lung from acute Bright's disease (see page 39) ; and clotting of blood in the pulmonary artery (see page 98).• These lesions are, however, exceptional, and the dyspncea they induce is not paroxysmal in the correct sense of the word ; for although the feeling of suffocation moderates, it does not entirely subside.